A wind turbine shall be marked and/or lighted if it is determined to be an obstacle.
Note 1.— Additional lighting or markings may be provided where in the opinion of the State such lighting or markings
are deemed necessary.
Recommendation.— When lighting is deemed necessary, in the case of a wind farm, i.e. a group of two or
more wind turbines, the wind farm should be regarded as an extensive object and the lights should be installed:
a) to identify the perimeter of the wind farm;
b) respecting the maximum spacing, in accordance with 184.108.40.206, between the lights along the perimeter, unless a
dedicated assessment shows that a greater spacing can be used;
c) so that, where flashing lights are used, they flash simultaneously throughout the wind farm;
d) so that, within a wind farm, any wind turbines of significantly higher elevation are also identified wherever they are located; and
e) at locations prescribed in a), b) and d), respecting the following criteria:
i) for wind turbines of less than 150 m in overall height (hub height plus vertical blade height), medium-intensity
lighting on the nacelle should be provided;
ii) for wind turbines from 150 m to 315 m in overall height, in addition to the medium-intensity light installed on
the nacelle, a second light serving as an alternate should be provided in case of failure of the operating light.
The lights should be installed to assure that the output of either light is not blocked by the other; and
iii) in addition, for wind turbines from 150 m to 315 m in overall height, an intermediate level at half the nacelle height of at least three low-intensity Type E lights, should be provided. If an aeronautical study shows that low-intensity Type E lights are not suitable, low-intensity Type A or B lights may be used.
Note.— The above e) does not address wind turbines of more than 315 m of overall height. For such wind
turbines, additional marking and lighting may be required as determined by an aeronautical study.
Recommendation.— The obstacle lights should be installed on the nacelle in such a manner as to provide an
unobstructed view for aircraft approaching from any direction.
Recommendation.— Where lighting is deemed necessary for a single wind turbine or short line of wind
turbines, the installation should be in accordance with e) or as determined by an aeronautical study.